Boron trifluoride recovery



United States.

. 3,012,859 BORON TRIFLUORIDE RECOVERY Harmon Madison Knight, La Marque, and Joe T. Kelly,

Dickinson, Tex., assignors, by mesne assignments, to

Standard Oil Company, Chicago, 111., a corporation of Indiana v No Drawing. FiledJune 17, 1958, Ser. No. 742,501

3 Claims. (Cl. 23-405) usually discarded because present procedures make it uneconomic to recover the BF content.

Another catalyst of considerable interest in hydrocarbon conversions is a complex between BF and metal salt hydrates. These complexes generally contain 1 mole of BF per mole of water of hydration. Once again it is very difiicult and an expensive proposition to release the BF from its complex and then recover the released BE, in a useable form.

An object of the invention is a method of releasing BF from its complexes with water, particularly, BF -hydrate and metal salt hydrate-BE, complex. A particular object is a method of recovering BF from spent catalyst containing BE, and water complexed with said BF Other objects will become apparent in the course of the detailed description.

It has been discovered that BF is displaced from a BF complex containing water by fluosulfonic acid. The released BF passes out of the complex containing zone in its natural state of a gas. The released BF may be readily recovered and used to prepare fresh complex.

The method of this invention is applicable to any complex which contains both BF and water; it appears that in such complexes the BE, is associated with the water and it is this association which must be broken in order to release the BF in the form of a gas. The method is particularly applicable to that form of BF and Water complex known as BF hydrate. The invention is applicable to either the BF monohydrate consisting of 1 mole of BF, per mole of water or the BF dihydrate consisting of 1 mole of BF per 2 moles of water. The method may be applied to the fresh BF -hydrate or it may be applied to BF hydrate which has been used as a catalyst until its catalytic powers have been lost, for example, a spent catalyst from the alkylation of benzene or toluene with diisobutylene using BF monohydrate catalyst.

Another complex to which the method is particularly applicable consists of a complex formed between BE, and a metal salt containing water of hydration. Examples of metal salt hydrates which form such complexes with BF are: ferrous pyrophosphate hydrate, nickel phosphate hydrate, aluminum pyrophosphate hydrate, etc. These complexes are solids at ordinary temperatures. When disassociated by heating to about the decomposition temperature of the hydrate the BF, is released in the form of a BF -hydrate complex. The method of the invention is applicable to either the metal salt hydrate- BF complex as such or to complexes which have become spent in catalytic operations. For example, ferric pyrophosphate hydrate-BF complex spent due to formation of a gummy coating thereon during the reaction of ethylone and isobutane to form gasoline boiling range hydrocarbons.

"' atent 3,012,859 Patented Dec. 12, 1961 It is to be understood. that. the, above specific embodiments of BF complexes containing water do not limit the scope of the invention and. the method is applicable. to any BF -eomplex containing water. v In the method of the. invention the water containing- BF -complex is contacted with a. fluosulfonic acid. 1 Apparently, the fiuosul'fonio acid forms a more stable complex with water than does BF, because BF is released from the complex in the form of gas. In order to release substantially all of the BF present in the complex at least about 1 mole of fluosulfonic acid must be used per mole of H 0 present in the release zone. It is preferred to use an excess of fluosulfonic acid in order to speed up the release reaction. This is particularly true when releasing BF from BF -hydrate. In general, it is preferred to use between 1.2 and 1.5 moles of fluosulfonic acid per mole of water in said hydrate.

The release reaction is carried out at temperatures between about 50 F. and 200 F. When it is desired to speed up the reaction it is preferred to operate at more elevated temperatures such as between about F. and F. The release reaction is carried out at normal pressure; however, higher pressures may be used when it is desired to minimize the amount of water taken overhead with the released BF The release reaction is carried out [for a time sutficient to release all of the BF theoretical releasable with the particular amount of fluosulfonic acid charged. When operating with the preferred amounts of fiuosulfonic acid substantially all the BF can be released and the reaction is carried out for the time needed to release substantially all the BE, present in the complex.

The method of the invention is illustrated by the following working examples:

Examples 1-2 These tests were made in a 500 ml. stirred Pyrex reactor in the following manner. Boron trifluoride monohydrate g.) was charged to the reactor. A mild vacuum was pulled through the scrubber system, which consisted of an oif-gas line from the top of the reactor to a trap, a series of three water scrubbers, then finally a calcium sulfate drier attached to a vacuum line. The stirrer was started, then fiuosulfonic acid was added at such a rate that the scrubbing system would remove the BF liberated from the complex. At the end of the run, the contents of the scrubbers were combined and analyzed for boron and sulfur.

Complete data for two runs are shown below where the results are based on boron analyses of aqueous solutions.

Example. 1 2

Run Conditions:

Temperature F. 65-74 140-160 Time, Total (minutes) 75 75 F8 A/BF, (molar) 1.3 1. 3 Mode of Operation:

Heat Added No Yes Stripping Used N 0 Yes Run Data:

BF; in Complex (g.) 134. 7 138. 1 Bli Liberated (g) 74. 5 132v 2 BF; Remaining in Reactor (g.). 54. 7 9. 2 BF; accounted For (g.) 129. 2 141. 4 Percent BF; Balance 96 102 Percent BF; Recovered 57. 7 93. 5

Example 3 In this example a complex consisting of ferric pyrophosphate containing 9 moles of water of hydration per mole of pyrophosphate and 9 moles of BF per mole of pyrophosphate was contacted with fluosulfonic acid in a Pyrex glass vessel. Large quantities of a White gas were released which gas was adsorbed in water. Analyses of the water solution showed the gas adsorbed to be boron 3. The method of claim 1 wherein said temperature is trifiuoride. r. r a. between about 130 F. and 170 F.

Thus having described the invention, what is claimed is:

l. A method of recovering BF from a complex consist- References Cited In the file of thls Patent ing of BB, and ferric pyrophosphate hydrate which 5 UNITED STATES PATENTS method comprises contacting said complex with at least 2 416 133 Young a1 18 19 47 about one mole of fluosulfonic acid per mole of ER, in 2628991 Schneider Feb 1953 said complex, at a temperature between about 50 F. and 2805982 Swimhart et a1 Sew 1957 200 F., for a time sufiicient to release substantially all of the 8P present and recovering the B1 so released. 10 OTHER REFERENCES 2. The method of claim 1 wherein said acid usage is Booth: Boron Trifluoride and Its Derivatives, 1949,

etween about 1.2 and 1.5 moles per mole of B1 present. page 8. 

1. A METHOD OF RECOVERING BF3 FROM A COMPLEX CONSISTING OF BF3 AND FERRIC PYROPHOSPHATE HYDRATE WHICH METHOD COMPRISES CONTACTING SAID COMPLEX WITH AT LEAST ABOUT ONE MOLE OF FLUOSULFONIC ACID PER MOLE OF BF3 IN SAID COMPLEX, AT A TEMPERATURE BETWEEN ABOUT 50*F. AND 200*F., FOR A TIME SUFFICIENT TO RELEASE SUBSTANTIALLY ALL OF THE BF3 PRESENT AND RECOVERING THE BF3 SO RELEASED. 